In recent years, there is a growing demand for a reduction in wiring capacities in order to achieve higher performance of multilayer wiring in large scale integrated circuits (LSIs). Here, to achieve the lowest wiring capacity, it is only necessary to form a hollow space between wires or a space between vias (an air gap, k=1.0). For example, the following technique is under study for forming such an air gap. First, wires are formed on a sacrificial film by a damascene method. Then the sacrificial film is removed. Thereafter, an insulating film having low step coverage is deposited so as to cover a gap between the wires. This method is indeed able to form an air gap between wires in a dense pattern because an upper part thereof is occluded before the gap is buried. However, if a large gap is formed by entirely removing the sacrificial film between wires in a sparse pattern, the insulating film is directly deposited in the location where the sacrificial film is removed. Accordingly, it is hardly possible to form an air gap.
Moreover, this conventional method has a problem if a position of a via hole formed on the wire is displaced when processing such a via hole. If the via hole is displaced and provided on an air gap formed in the lower layer, a via contact material is deposited also inside the air gap. This may cause an insulation failure between the wires. Such performance degradation is a critical issue in a dense pattern where lines and spaces are formed in a width dimensional ratio of 1:1. It is predicted that such misalignment will be a serious problem along with future refinement of multilayer wiring.